What does it mean when your LTFT is negative?
If the LTFT is negative, it means the ECU has been reducing fuel to maintain an ideal fuel mix. Which basically means the car is running rich. If LTFT is positive, it means the ECU is adding fuel which is an indication that the car is running lean. Normally LTFT should be between -10 to +10 percent.
What causes a significant increase in STFT and LTFT?
A significant increase in STFT and LTFT can be caused by: 1 Unmeasured air is entering the engine due to a vacuum leak (higher fuel trim at idle, but less at higher RPMs) 2 Incorrectly reporting sensors (dirty MAF reporting less airflow) 3 Dirty or blocked fuel injectors
Why are STFT’s almost always positive between two banks?
STFT’s between two banks are almost identical and are almost always positive, meaning ECU is adjusting for a lean condition, which by the way should be normal since I have an aftermarket CAI that is obviously allowing much more air into the engine causing more fuel to be matched (that’s my understanding).
Is the STFT a positive or negative number?
Not only are the STFT’s positive (they are usually around +2.0% to +4.0%), but they are also very close to each other.
How to evaluate the situation between LTFT and STFT?
How to evaluate the situation, if LTFT of one bank is with a positive sign (DME enriches fuel mixture), but LTFT of second bank is with a negative sign (DME makes fuel mixture leaner)? This situation is normal and shows, that existing situation is close to perfect. If the difference between LTFT of banks is in correct values – perfect!
STFT’s between two banks are almost identical and are almost always positive, meaning ECU is adjusting for a lean condition, which by the way should be normal since I have an aftermarket CAI that is obviously allowing much more air into the engine causing more fuel to be matched (that’s my understanding).
Not only are the STFT’s positive (they are usually around +2.0% to +4.0%), but they are also very close to each other.
Why do I get negative LTFT on my M5?
Negative LTFT’s with the engine warm, low RPM. In other words, if left uncorrected, the engine would be running too rich. Common reasons for this include over-reading MAF’s, excessive fuel rail pressure and leaky fuel injectors. I don’t see how a fresh-from-Bavaria M5 would suffer from any of these.